首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   259篇
  免费   11篇
  国内免费   5篇
耳鼻咽喉   1篇
儿科学   4篇
妇产科学   16篇
基础医学   22篇
口腔科学   6篇
临床医学   25篇
内科学   98篇
皮肤病学   4篇
神经病学   21篇
特种医学   5篇
外科学   32篇
综合类   1篇
预防医学   11篇
眼科学   3篇
药学   8篇
肿瘤学   18篇
  2024年   2篇
  2023年   4篇
  2022年   2篇
  2021年   12篇
  2020年   2篇
  2019年   7篇
  2018年   5篇
  2017年   6篇
  2016年   13篇
  2015年   18篇
  2014年   20篇
  2013年   14篇
  2012年   26篇
  2011年   17篇
  2010年   5篇
  2009年   7篇
  2008年   18篇
  2007年   15篇
  2006年   22篇
  2005年   14篇
  2004年   16篇
  2003年   13篇
  2002年   8篇
  2001年   2篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1984年   2篇
排序方式: 共有275条查询结果,搜索用时 15 毫秒
1.
High adherence to the Mediterranean diet (MD) has been associated with a lower prevalence of Metabolic Syndrome (MetS). The present study aimed to investigate the impact of MD adherence on parameters of MetS. A systematic literature search was performed in PubMed, Cochrane Central Registry of Clinical Trials (CENTRAL), Scopus, EMBASE, Web of Science and Google Scholar databases. Observational studies that recorded adherence to MD and components/measures of the MetS, such as waist circumference (WC), blood pressure (BP), fasting blood glucose (FBG), high-density lipoprotein (HDL) cholesterol and triglycerides (TG), were included in this study. A total of 58 studies were included in our study. WC and TG were significantly lower in the high adherence MD group (SMD: −0.20, (95%CI: −0.40, −0.01), SMD: −0.27 (95%CI: −0.27, −0.11), respectively), while HDL cholesterol was significantly higher in the same group (SMD: −0.28 (95%CI: 0.07, 0.50). There was no difference in FBG and SBP among the two groups (SMD: −0.21 (95%CI: −0.54, 0.12) & SMD: −0.15 (95%CI: −0.38, 0.07), respectively). MD may have a positive impact on all parameters of MetS. However, further research is needed in this field.  相似文献   
2.
BACKGROUND: Telomerase preserves telomeres' function and structure preventing cellular senescence. Its activity is reduced in peripheral blood mononuclear cells (PBMC) of haemodialysis (HD) patients. The purpose of this study is to investigate the potential correlation between increased oxidative stress/inflammation and telomerase activity in PBMC of HD patients. METHODS: Telomerase activity was measured by PCR-ELISA in PBMC isolated from a group of 42 HD patients and 39 subjects with estimated glomerular filtration rate >or=80 mL/min (control group). Serum oxidized low-density lipoprotein (ox-LDL), tumour necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) were also measured in both groups by ELISA. RESULTS: Ox-LDL was negatively correlated to percentage telomerase activity in PBMC (r = -0.506, P = 0.000 in the whole group of 81 HD and normal subjects and r = -0.559, P < 0.001 in HD patients). TNF was also inversely associated with percentage telomerase activity in the whole group studied (r = -0.492, P = 0.000) while IL-10 was not. In stepwise multiple linear regression, taking into consideration the most important characteristics of the HD patients and control group, the only significant predictors for percentage telomerase activity in PBMC were ox-LDL and TNF (beta = -0.421, t = -4.083, P = 0.000 and beta = -0.381, t = -3.691, P = 0.000, respectively) while examining separately HD patients, the predictors for the same parameter were ox-LDL and HD duration (beta = -0.671, t = -4.709, P = 0.000 and beta = -0.349, t = -2.447, P = 0.023, respectively). CONCLUSION: Ox-LDL serum level is inversely correlated to telomerase activity in PBMC of HD patients. Our study proposes a new consequence of increased oxidative stress in HD patients: the premature cellular senescence potentially related to atherosclerosis through LDL oxidation.  相似文献   
3.
Oxidized organic aerosol (OOA) is a major component of ambient particulate matter, substantially impacting climate, human health, and ecosystems. OOA is readily produced in the presence of sunlight, and requires days of photooxidation to reach the levels observed in the atmosphere. High concentrations of OOA are thus expected in the summer; however, our current mechanistic understanding fails to explain elevated OOA during wintertime periods of low photochemical activity that coincide with periods of intense biomass burning. As a result, atmospheric models underpredict OOA concentrations by a factor of 3 to 5. Here we show that fresh emissions from biomass burning exposed to NO2 and O3 (precursors to the NO3 radical) rapidly form OOA in the laboratory over a few hours and without any sunlight. The extent of oxidation is sensitive to relative humidity. The resulting OOA chemical composition is consistent with the observed OOA in field studies in major urban areas. Additionally, this dark chemical processing leads to significant enhancements in secondary nitrate aerosol, of which 50 to 60% is estimated to be organic. Simulations that include this understanding of dark chemical processing show that over 70% of organic aerosol from biomass burning is substantially influenced by dark oxidation. This rapid and extensive dark oxidation elevates the importance of nocturnal chemistry and biomass burning as a global source of OOA.

Highly oxidized organic aerosol (OOA) is a dominant component of particulate matter air pollution globally (13); however, sources of OOA remain uncertain, limiting the ability of models to accurately represent OOA and thus predict the associated climate, ecosystem, and health implications (4, 5). The current conceptual model of OOA formation suggests that anthropogenic OOA predominantly originates from the oxidation of volatile (VOCs), intermediate volatility (IVOCs), and semivolatile (SVOCs) organic compounds by the OH radical, resulting in lower-volatility products that condense to the particle phase (6). As the OH radical is formed through photolysis and has a very short atmospheric lifetime [less than a second (7)], this oxidation mechanism only occurs in the presence of sunlight. Further, the time scale for OOA formation through oxidation with OH in models is on the order of a few days (8). While this understanding is sufficient in explaining OOA concentrations in summer or periods with high solar radiation, atmospheric models fail to reproduce the observed concentration of OOA in the ambient atmosphere during winter and low-light conditions (9, 10). Fountoukis et al. (9) found simulated OOA concentrations significantly underestimated in wintertime Paris. Tsimpidi et al. (10) also reported an underprediction of simulated OOA globally in winter, suggesting missing sources of both primary OA (POA) and secondary formation pathways. This underproduction suggests a possible overlooked conversion pathway of organic vapors or particles to OOA that is not accounted for in current chemical transport and climate models.As stricter controls on fossil fuel combustion are implemented, residential biomass burning (BB) as a source of heating or cooking is becoming an increasingly important source of OA in urban environments (1, 11, 12). Further, increasing rates of wildfires from climate change are increasing the frequency of smoke-impacted days in urban areas (1214). BB emissions include high concentrations of POA, SVOCs, IVOCs, and VOCs (15, 16), thus making BB a key source of OOA. Previous research has focused on quantifying the concentration of OOA formed through photochemical oxidation reactions (i.e., OH) with BB emissions (17, 18). However, oxidation of BB emissions in low or no sunlight is less well understood and is not included in chemical transport models. As opposed to OH, the NO3 radical is formed through reactions with NO2 and O3 and is rapidly lost in the presence of sunlight (19). Thus, the NO3 radical is only available in significant concentrations at night or other low-light conditions (20, 21). Previous research has established that biogenic VOCs may undergo oxidation at night when mixed with anthropogenic emissions containing NO2 and O3 (19, 2227). There have been only a few studies that consider that nighttime oxidation of residential wood combustion may proceed through similar pathways (2831); however, the magnitude and relevance to observed OOA in the ambient atmosphere has not yet been established. By combining laboratory experiments and ambient observations to inform a chemical transport model, we present strong evidence that nighttime oxidation of BB plumes (proceeding through reactions with O3 and the NO3 radical) is an important source of OOA.  相似文献   
4.
5.
OBJECTIVES: Hepatic steatosis is a common feature of chronic hepatitis C. The purpose of this study was to determine factors related to the presence of steatosis and to define the role of steatosis in the response to antiviral treatment in chronic hepatitis C patients. METHODS: We retrospectively analysed all patients with chronic hepatitis C treated in a 5 year period in our department. Patients were included in the study only if a pretreatment liver biopsy specimen was available for evaluation. All patients treated either with interferon in combination with ribavirin, or with pegylated interferon in combination with ribavirin were included irrespectively of their response (early, end of treatment and/or sustained) to antiviral therapy. RESULTS: A total of 116 patients with chronic hepatitis C were included in the study with a mean age of 45.5 +/- 14.1 years. Steatosis was present in 52 patients (44.8%). On univariate analysis age, P = 0.04 and body mass index > or = 25, P = 0.004 were correlated with the presence of steatosis and on multivariate analysis only body mass index > or = 25, P = 0.032. Advanced fibrosis was not found associated with steatosis. Sixty patients out of 116 (51.7%) had sustained virological response (SVR). In particular 42 out of 64 patients with no steatosis (65.6%) had SVR compared to 20 out of 52 patients (38.4%) with any degree of steatosis (P = 0.009). Patients with genotype 2 or 3 had a more favourable outcome compared to patients with 1 or 4 genotypes, 63.2% vs 49.2%, P = 0.032. Also increased age (P = 0.0001), gamma glutamyltransferase (GGT) (P = 0.029), no history of intravenous drugs use (P = 0.001) and advanced fibrosis on pretreatment biopsy (P = 0.046) were correlated with treatment failure. On multivariate analysis significant independent association with SVR was found with the presence of steatosis on pretreatment biopsy (P = 0.004), increased GGT (P = 0.005) and genotype (P = 0.017). CONCLUSION: Steatosis in the liver biopsy performed before the beginning of antiviral treatment was found to be associated only to the body mass index of the patients and to be a strong independent factor for treatment failure.  相似文献   
6.
7.
8.
Osteoarthritis (OA) is a major cause of suffering for millions of people. Investigating the disease directly on humans may be challenging. The aim of the present study is to investigate the advantages and limitations of the animal models currently used in OA research. The animal models are divided into induced and spontaneous. Induced models are further subdivided into surgical and chemical models, according to the procedure used to induce OA. Surgical induction of OA is the most commonly used procedure, which alters the exerted strain on the joint and/or alter load bearing leading to instability of the joint and induction of OA. Chemical models are generated by intra-articular injection of modifying factors or by systemically administering noxious agents, such as quinolones. Spontaneous models include naturally occurring and genetic models. Naturally occurring OA is described in certain species, while genetic models are developed by gene manipulation. Overall, there is no single animal model that is ideal for studying degenerative OA. However, in the present review, an attempt is made to clarify the most appropriate use of each model.  相似文献   
9.
Violent incidents in acute inpatient units for children and adolescents are a major and persistent problem. The demographic, clinical, and modifiable (environmental–organizational) risk factors that affect inpatient violence in an Acute Child and Adolescent Psychiatric Unit were investigated via a retrospective study. Data were collected from nursing and medical reports and the unit's census and included 100 days per year for 16 years. Incidents of violence and assault types were recorded, and variables such as the diagnostic category of assailants, total number of patients, and staffing factors during the incident were examined. Of the 2390 violent incidents recorded, 50% were attributed to cases of physical violence towards another patient, 17% to physical violence towards nursing staff, 19% to physical violence towards self and 14% to destruction of property. According to the final multivariable model, for each additional patient in the unit, the risk of a violent event increased by 9.51%; for each additional offender patient, the risk increased by 14.06%; the number of assistant nurses was associated with a 25.03% increased risk; and, after 2006, the risk increased by 68.99%. The most significant factor associated with a 59.98% decreased risk was the total number of nursing staff. All variables significantly and independently contributed to the model. Acute inpatient psychiatric units with a small number of hospitalized patients, adequate, well‐trained and specialized nursing staff, and the hospitalization of different types of patients in separate wards or units are expected to facilitate a reduction in the frequency of violent incidents.  相似文献   
10.
Next-generation sequencing has revealed novel recurrent mutations in chronic lymphocytic leukemia, particularly in patients with aggressive disease. Here, we explored targeted re-sequencing as a novel strategy to assess the mutation status of genes with prognostic potential. To this end, we utilized HaloPlex targeted enrichment technology and designed a panel including nine genes: ATM, BIRC3, MYD88, NOTCH1, SF3B1 and TP53, which have been linked to the prognosis of chronic lymphocytic leukemia, and KLHL6, POT1 and XPO1, which are less characterized but were found to be recurrently mutated in various sequencing studies. A total of 188 chronic lymphocytic leukemia patients with poor prognostic features (unmutated IGHV, n=137; IGHV3-21 subset #2, n=51) were sequenced on the HiSeq 2000 and data were analyzed using well-established bioinformatics tools. Using a conservative cutoff of 10% for the mutant allele, we found that 114/180 (63%) patients carried at least one mutation, with mutations in ATM, BIRC3, NOTCH1, SF3B1 and TP53 accounting for 149/177 (84%) of all mutations. We selected 155 mutations for Sanger validation (variant allele frequency, 10–99%) and 93% (144/155) of mutations were confirmed; notably, all 11 discordant variants had a variant allele frequency between 11–27%, hence at the detection limit of conventional Sanger sequencing. Technical precision was assessed by repeating the entire HaloPlex procedure for 63 patients; concordance was found for 77/82 (94%) mutations. In summary, this study demonstrates that targeted next-generation sequencing is an accurate and reproducible technique potentially suitable for routine screening, eventually as a stand-alone test without the need for confirmation by Sanger sequencing.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号